Rotor provided with shaft pivots

ABSTRACT

A rotor (2, 3) is provided with bearing trunnions (4, 5). The rotor is made of a material with limited strength properties, such as aluminum. At least one of the bearing trunnions (4) comprises a concentric sleeve (20) made of steel at one end of the rotor. The inner end (21) of the sleeve (20) is radially attached to the rotor end (22) by a trunnion (4) protruding into the sleeve, or by a groove (40) in the rotor end (22), into which groove the inner end (21) of the sleeve protrudes. The outer end of the sleeve (20) is kept by a screw (25, 27) screwed into the rotor (2, 3) and provided with a screw head (24) pressed axially in the direction towards the rotor end (22).

BACKGROUND OF THE INVENTION

The present invention relates to rotor provided with bearing trunnions,which rotor is made of lightweight material having limited strengthproperties.

When rotors are made of a material with limited strength properties incomparison to steel, some problems are involved in the provision of thebearing trunnions. If the bearing trunnions are made of the samematerial as the rotors and integrated with the rotors, e.g. of aluminum,magnesium, plastics or ceramic material, the bearing trunnions will getan unpractically large diameter and so also the bearings. Thisdisadvantage is particularly obvious at journalling of the low pressureends of the rotors in screw compressors provided with axial inlet ports,the design of which is restricted by bearing trunnions and bearingshaving a large diameter. The provision of axially positioned screws forreinforcing the bearing trunnions has been tested, but this has not beensufficient for avoiding harmful flexural stresses to the bearingtrunnions. Steel shafts passing through especially plastic rotors havebeen used, resulting in sufficient bending strength, but at the sametime resulting in an increased rotor weight where low weight is desired.

The object of the present invention is to achieve in a simple way rotorshaving bearing trunnions which have a comparatively small diameter butat the same time a great strength property, especially bending strength.

SUMMARY OF THE INVENTION

According to the present invention, a rotor is provided with a pluralityof bearing trunnions (4,5). The rotor is made of a lightweight materialhaving limited strength properties. At least one (4) of the trunnions(4, 5) comprises a concentric sleeve (20) located at one end of therotor. The sleeve (20) has an inner end (21) which is radially fixed bya guide (4,40) at the one end (22) of the rotor, and the sleeve (20) hasan outer end positioned by a clamping surface (23) acted upon by a head(24) of a screw (25) that extends into a threaded boring (28) in the oneend of the rotor. the head (24) of the screw bears axially against theouter end of the sleeve (20) and keeps the sleeve (20) pressed againstthe one end (22) of the rotor.

According to a preferred embodiment of the invention, the sleevecomprises an inner race of a radial bearing (30).

According to another embodiment of the invention, the guide comprises ahollow trunnion (4) protruding from the one end of the rotor, and thehollow trunnion has essentially the same outer diameter as the innerdiameter of the sleeve (20).

According to an alternative embodiment of the invention, the guidecomprises an annular groove (40) in the one end of the rotor, into whichgroove (40) the inner end portion (21) of the sleeve protrudes.

According to another feature of the invention, the screw head (24) hasan underside which is provided with an alignment spacer (29) whichprotrudes into the outer end of the sleeve (20). The spacer preferablyhas an outer diameter which is substantially the same as the innerdiameter of the outer end of the sleeve for close engagement with thesleeve and for centering the sleeve. The spacer (29) faces the clampingsurface (23) on the underside of the screw head (24).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in further detail below with reference to theappended drawings, which show various embodiments of rotors according tothe invention;

FIG. 1 is a side view of a screw compressor with a housing, bearings andclutch, shown in section,

FIG. 2 is a detail of FIG. 1 shown on a larger scale, and

FIG. 3 is a modification of the embodiment shown in FIG. 2.

DETAILED DESCRIPTION

FIG. 1 shows a screw compressor with a housing 1, in which a male rotor2 and a female rotor 3 are journalled with bearing trunnions 4 and 5,respectively, in a low pressure end wall 6 and a high pressure end wall7.

Each bearing trunnion 5 is journalled in a combined thrust and radialbearing 8 whose inner race 9 together with a spacer sleeve 10 abut thebearing trunnion 5 and are kept pressed against the corresponding rotorend by a screw 11 screwed into the corresponding rotor 2,3 and having ahead 12 that is pressing a synchronizing gear 13 and 14, respectively,against the inner races 9 of the bearings 8. The female rotor 3 and itssynchronizing gear 14 are via a disc clutch 15 driven by a belt pulley16 connected to the clutch.

The journalling of the bearing trunnions 4 in the end wall 6 is shownmost clearly in FIG. 2. The bearing trunnion 4 is with close running fitenclosed by a steel sleeve 20, the inner end of which abuts the endsurface 22 of the rotor 2 fixed in the radial direction by the bearingtrunnion 4.

The outer end of the sleeve 20 protrudes beyond the end of the bearingtrunnion 4 and abuts an annular, plane surface 23 of a head 24 of ascrew 25 that extends through an axial boring 26 in the bearing trunnion4 and with a threaded part 27 extends into a threaded boring 28. Thehead 24 of the screw is provided with a circular spacer 29 that extendsinto the outer end of the sleeve 20 for centering purposes.

The sleeve 20 comprises of the inner race of a radial bearing 30 havingan outer race 31 abutting a cylindrical wall 32 in a cavity in the endwall 6.

By the radial positioning of the sleeve 20 at the rotor end 22 by theinner part of the bearing trunnion 4 and the pressure of the screw head24 against the outer end of the sleeve 20 and the centering of this bythe circular spacer 29, shear stresses as well as flexural stressesacting on this part of the journalling of the rotor will be carried bythe sleeve 20 and the axial pressure of the screw 25 against the sleeve20. The diameter of the sleeve 20 accordingly can be essentially smallerthan the diameter of a bearing trunnion made of e.g. aluminum.

The bearing trunnion 4 in the sleeve 20 shown in FIG. 2 is intended onlyfor radial positioning of the inner end of the sleeve 20 with respect tothe end of the rotor.

Therefore, the bearing trunnion 4 can be made much shorten, whichinvolves an essential material saving at the manufacturing of the rotor.It is even possible to completely spare the bearing trunnion if apositioning of the inner end 21 of the sleeve 20 can be achieved inanother way.

Such an embodiment is shown in FIG. 3, which differs from the embodimentin FIG. 2 in that the bearing trunnion 4 is eliminated and replaced byan annular groove 40 in the end surface 22 of the rotor 2, in whichgroove the inner end 21 of the sleeve 20 is situated and radially fixed.

The journalling of the bearing trunnion 5 in FIG. 1 is carried outessentially in the same way as the journalling of the bearing trunnion 4in FIGS. 1 and 2. Instead of a sleeve 20 made in one piece and enclosingthe bearing trunnion 4, the bearing trunnion 5 is positioned partly inthe sleeve 10, and partly in the inner race 9 of the bearing 8. At axialcompression of these by the screw 11, the sleeve 10 and the inner race 9will work like a single sleeve corresponding to the sleeve 20 of thebearing trunnion 4.

What is claimed is:
 1. A rotor provided with a plurality of bearingtrunnions (4,5), wherein:said rotor is made of a lightweight materialhaving limited strength properties, at least one (4) of the trunnions(4, 5) comprises a concentric sleeve (20) located at one end of therotor, the sleeve (20) having an inner end (21) which is radially fixedby a guide (4,40) at the one end (22) of the rotor and the sleeve (20)having an outer end positioned by a clamping surface (23) acted upon bya head (24) of a screw (25) that extends into a threaded boring (28) insaid one end of the rotor, and wherein the head (24) of the screw bearsaxially against the outer end of the sleeve (20) and keeps the sleeve(20) pressed against said one end (22) of the rotor.
 2. A rotoraccording to claim 1, wherein said lightweight material is a lightweightmetal.
 3. A rotor according to claim 1, wherein said concentric sleeve(20) is made of steel.
 4. A rotor according to claim 1, wherein saidconcentric sleeve (20) is made of a material which is stronger than saidlightweight material of said rotor.
 5. A rotor according to claim 1,wherein the sleeve (20) comprises an inner race of a radial bearing(30).
 6. A rotor according to claim 5, wherein the guide comprises ahollow trunnion (4) protruding from said one end of the rotor, andwherein said hollow trunnion (4) has essentially the same outer diameteras the inner diameter of the sleeve (20).
 7. A rotor according to claim6, wherein the sleeve (20) comprises an inner race of a radial bearing(30).
 8. A rotor according to claim 7, wherein the guide comprises ahollow trunnion (4) protruding from said one end of the rotor, andwherein said hollow trunnion (4) has essentially the same outer diameteras the inner diameter of the sleeve (20).
 9. A rotor according to claim1, wherein the guide comprises a hollow trunnion (4) protruding fromsaid one end of the rotor, and wherein said hollow trunnion (4) hasessentially the same outer diameter as the inner diameter of the sleeve(20).
 10. A rotor according to claim 3, wherein the guide comprises ahollow trunnion (4) protruding from said one end of the rotor, andwherein said hollow trunnion (4) has essentially the same outer diameteras the inner diameter of the sleeve (20).
 11. A rotor according to claim4, wherein the guide comprises a hollow trunnion (4) protruding fromsaid one end of the rotor, and wherein said hollow trunnion (4) hasessentially the same outer diameter as the inner diameter of the sleeve(20).
 12. A rotor according to claim 1, wherein the guide comprises anannular groove (40) in said one end of the rotor, into which groove theinner end portion (21) of the sleeve protrudes.
 13. A rotor according toclaim 2, wherein the guide comprises an annular groove (40) in said oneend of the rotor, into which groove the inner end portion (21) of thesleeve protrudes.
 14. A rotor according to claim 4, wherein the guidecomprises an annular groove (40) in said one end of the rotor, intowhich groove the inner end portion (21) of the sleeve protrudes.
 15. Arotor according to claim 1, wherein said screw head (24) has an underside which is provided with an alignment spacer (29) which protrudesinto the outer end of the sleeve (20), the spacer (29) having an outerdiameter which is substantially the same as the inner diameter of theouter end of the sleeve for centering the sleeve, and said spacer (29)facing said clamping surface (23) on the under side of said screw head(24).
 16. A rotor according to claim 2, wherein said screw head (24) hasan under side which is provided with an alignment spacer (29) whichprotrudes into the outer end of the sleeve (20), the spacer (29) havingan outer diameter which is substantially the same as the inner diameterof the outer end of the sleeve for centering the sleeve, and said spacer(29) facing said clamping surface (23) on the under side of said screwhead (24).
 17. A rotor according to claim 4, wherein said screw head(24) has an under side which is provided with an alignment spacer (29)which with close alignment protrudes into the outer end of the sleeve(20), the spacer (29) having an outer diameter which is substantiallythe same as the inner diameter of the outer end of the sleeve forcentering the sleeve, and said spacer (29) facing said clamping surface(23) on the under side of said screw head (24).
 18. A rotor according toclaim 5, wherein said screw head (24) has an under side which isprovided with an alignment spacer (29) which protrudes into the outerend of the sleeve (20), the spacer (29) having an outer diameter whichis substantially the same as the inner diameter of the outer end of thesleeve for centering the sleeve, and said spacer (29) facing saidclamping surface (23) on the under side of said screw head (24).
 19. Arotor according to claim 6, wherein said screw head (24) has an underside which is provided with an alignment spacer (29) which protrudesinto the outer end of the sleeve (20), the spacer (29) having an outerdiameter which is substantially the same as the inner diameter of theouter end of the sleeve for centering the sleeve, and said spacer (29)facing said clamping surface (23) on the under side of said screw head(24).
 20. A rotor according to claim 7, wherein said screw head (24) hasan under side which is provided with an alignment spacer (29) whichprotrudes into the outer end of the sleeve (20), the spacer (29) havingan outer diameter which is substantially the same as the inner diameterof the outer end of the sleeve for centering the sleeve, and said spacer(29) facing said clamping surface (23) on the under side of said screwhead (24).
 21. A rotor according to claim 8, wherein said screw head(24) has an under side which is provided with an alignment spacer (29)which protrudes into the outer end of the sleeve (20), the spacer (29)having an outer diameter which is substantially the same as the innerdiameter of the outer end of the sleeve for centering the sleeve, andsaid spacer (29) facing said clamping surface (23) on the under side ofsaid screw head (24).
 22. A rotor according to claim 9, wherein saidscrew head (24) has an under side which is provided with an alignmentspacer (29) which protrudes into the outer end of the sleeve (20), thespacer (29) having an outer diameter which is substantially the same asthe inner diameter of the outer end of the sleeve for centering thesleeve, and said spacer (29) facing said clamping surface (23) on theunder side of said screw head (24).
 23. A rotor according to claim 10,wherein said screw head (24) has an under side which is provided with analignment spacer (29) which protrudes into the outer end of the sleeve(20), the spacer (29) having an outer diameter which is substantiallythe same as the inner diameter of the outer end of the sleeve forcentering the sleeve, and said spacer (29) facing said clamping surface(23) on the under side of said screw head (24).
 24. A rotor according toclaim 11, wherein said screw head (24) has an under side which isprovided with an alignment spacer (29) which protrudes into the outerend of the sleeve (20), the spacer (29) having an outer diameter whichis substantially the same as the inner diameter of the outer end of thesleeve for centering the sleeve, and said spacer (29) facing saidclamping surface (23) on the under side of said screw head (24).
 25. Arotor according to claim 12, wherein said screw head (24) has an underside which is provided with an alignment spacer (29) which protrudesinto the outer end of the sleeve (20), the spacer (29) having an outerdiameter which is substantially the same as the inner diameter of theouter end of the sleeve for centering the sleeve, and said spacer (29)facing said clamping surface (23) on the under side of said screw head(24).
 26. A rotor according to claim 13, wherein said screw head (24)has an under side which is provided with an alignment spacer (29) whichprotrudes into the outer end of the sleeve (20), the spacer (29) havingan outer diameter which is substantially the same as the inner diameterof the outer end of the sleeve for centering the sleeve, and said spacer(29) facing said clamping surface (23) on the under side of said screwhead (24).
 27. A rotor according to claim 14, wherein said screw head(24) has an under aide which is provided with an alignment spacer (29)which protrudes into the outer end of the sleeve (20), the spacer (29)having an outer diameter which is substantially the same as the innerdiameter of the outer end of the sleeve for centering the sleeve, andsaid spacer (29) facing said clamping surface (23) on the under aide ofsaid screw head (24).